The present invention is directed to the field of ozone decomposition. In particular, the present invention is directed to an ozone filter having a carrier composed of paper made of inorganic fibers impregnated with a solution of fine powder-like active manganese dioxide, thereby providing a high-performance ozone filter which is suitable for use in preventing emission of ozone.
Due to the powerful oxidizing action of ozone, it is useful in sterilization, disinfection, and other treatment applications. Ozone is also utilized extensively in the field of medical treatment and food preparation. Although ozone has many useful applications, ozone can be very harmful to human life. For example, the toxicity exhibited by ozone causes irritation in the human respiratory system if the toxicity concentration in the air exceeds 0.1 particles per million (ppm), and endangers human life if it exceeds 50 ppm. The amount of ozone in the air has increased in recent years due to the production of ozone by machines such as electrostatic copying machines and the like. It is therefore desirable to develop a simple method of decomposing ozone in the air.
Conventionally, ozone processing technologies include an activated carbon adsorption process, a thermal decomposition process, a wet process, and a contact decomposition process. The contact decomposition process is advantageous in many respects because it is extremely safe, can be carried out at ordinary temperatures, and can be carried out easily on a small scale.
Manganese dioxide is conventionally used as a decomposing catalyst, as shown by, for example, Japanese Patent Application Laid-Open No. 4094/1976, Japanese Patent Application Publication No. 8456/1980, and Japanese Patent Application Laid-Open No. 245850/1989. In addition, a nickel-based catalyst has been used as a decomposing catalyst. The manganese dioxide-based catalysts, however, are more advantageous in terms of cost. In an ozone decomposing reaction, as well as a vapor-phase-contact decomposing reaction, it is desirable to attain a high reaction rate by causing the processed gas and the catalyst to positively contact each other, while minimizing any pressure loss thereby resulting. Thus, it is necessary to use a highly activated catalyst, and carefully monitor the method used to bring the processed gas into contact with the catalyst. Ozone filters used to decompose ozone in the air generated by office machines and the like are restricted in terms of size and level of noise produced. As the ozone concentration in the air is ordinarily very low, it is particularly important that a large volume of air be processed with a small amount of catalyst at a high reaction rate and a reduced pressure loss using such ozone filters. Typically, such ozone filters have a catalyst that is carried by a carrier with a honeycomb structure.